Vehicles with direct injection engines typically include a fuel rail for delivery of pressurized fuel to a plurality of injectors, wherein each of the injectors is coupled to a cylinder head for direct injection of fuel into an engine cylinder. Due to high operating fuel pressure and direct coupling of injectors to cylinder heads, undesirable structureborne noise may be generated during idle operation of the vehicle. High frequency energy may be transmitted from the injector to the cylinder head. Specifically, a “ticking” noise may be generated because of high frequency energy caused by impact between the magnetic solenoid valve armature and stopper at injector opening, and pin and seat at injector closing. This noise may be audible to an operator when the engine is at idle, and produces little background noise.
In one approach, described in US Patent Application Publication US2009/0071445, a steel dampening element is disposed between a conical region of injection valve and a cylinder head. The dampening element has a conical shape and a central pass through wherein the injector is fitted. A top portion of the dampening element includes an elevation, such as an annular flange, which abuts the injector. A diameter of the dampening element is less than a diameter of the cylinder head, such that a first gap is exists between the support element and the cylinder head. A second gap exists between a lower portion of the support element and the injector, below a line of contact/abutment between the injector and the annular flange. A force from the injector may bend the top portion of the dampening element outward generating radial displacement into the first gap in order to absorb a portion of the impact. Thus, during operation of the vehicle, periodic pulses of the injector are transferred to the cylinder head in an attenuated fashion.
The inventors herein recognize potential issues with such a configuration for a dampening element. As one example, an outer wall of the top portion of the previously described dampening element may impact an inner wall of the cylinder head at a specific line of contact during radial displacement. In cases where the cylinder head is comprised of aluminum, the steel dampening element may damage the inner wall of the cylinder head over time. In another example, much of the elastic deformation of the previously described dampening element may be absorbed at a joint between the upper portion and a lower portion. In this example, the joint may be weakened over time and may eventually be deformed or broken.
Thus, some of the above issues may be at least partly addressed by a direct fuel injection cylinder of an engine, comprising, a cylinder head including an injector bore with a shelf; a high-pressure direct injector disposed in the injector bore; and a spring washer disposed between the high-pressure direct injector and the shelf with the high-pressure direct injector positioned through a central pass-through of the spring washer, the spring washer forming a conical wall with a plurality of waves.
In this example, the spring washer includes a series of regular waves, and inner-facing troughs of the waves contact the injector in the non-compressed state. In order to absorb impact of the injector, each of the waves may be elastically deformed from the non-compressed state into the compressed state. Therefore, elastic deformation is distributed over a larger surface area than that of the previously described dampening element. In the compressed state, outer-facing crests of the waves may contact the cylinder head. Impact of the spring washer against the wall of the cylinder head is distributed over a larger surface area and may decrease damage to the inner wall of the cylinder head. Further, the cone may be elastically deformed by the introduction of hoop stress. As such, an angle at the intersection of an inner side of the spring washer and the shelf in the injector bore has first magnitude in the non-compressed state and a second magnitude in the compressed state. In this example, the first magnitude is less than the second magnitude.
In one specific example, a spring washer includes a conical wall encompassing a central pass-through, the conical wall comprising a plurality of regular waves. In this example, the waves are beveled such that a crest of a wave and a trough of a wave are substantially flat. The crests and the troughs are joined via connecting walls. The connecting walls intersect each of the crests and troughs at an equal angle, and the angle may be greater in the compressed state than the non-compressed state. As such, during operation of the direct injection fuel system, elastic deformation is absorbed by the dampening element at each of the lines of intersection between the angled flat portions and each of the crests and troughs. Further, the cone may absorb impact via hoop stress.
Combined these features provide a spring washer which distributes elastic deformation over a greater surface area, and therefore the spring washer may have increased durability. Additionally, impact of the spring washer against the surface of the cylinder head is distributed over a larger surface area, and therefore over time the spring washer may limit damage to the surface of the cylinder head.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.